Field of the Invention
The invention relates to a semiconductor component having a housing, a carrier plate, and at least one ceramic substrate, which is provided with a metalization layer at least at its top side. Furthermore, the semiconductor component has at least two switching elements, which are disposed in an electrically conductive manner on the top side of the ceramic substrate and each have load current connections and a control connection. Moreover, provision is made of load current connection elements on a first side and a second side, opposite to the first side, which are electrically connected to the load current connections of the switching elements via leads. In this case, the load current connection elements may have a first or a second supply potential.
Semiconductor components of this type are used for example in motor vehicles between at least one battery-backed low-voltage on-board electrical system, and a starter-generator as a starter or a charging device for the respective battery. They serve, during overrun operation of the motor vehicle, for adapting voltage and power of the starter-generator, which then operates as a generator, to the corresponding operating data of the respective battery to be recharged and, during starting of the starter-generator, which then operates as a motor, with the aid of the respective battery, for ensuring a sufficient starting torque with a correspondingly high starting current.
Essential structural parts of such a circuit configuration are held to be, in particular, a number of semiconductor half-bridges as power structural parts, a number of intermediate circuit components, in particular capacitors, and a number of control elements, in particular driver stages. A semiconductor component of this type is disclosed in German Patent DE 196 45 636 C1, for example, which component serves for driving an electric motor.
The semiconductor components described often have MOSFETs as the switching elements. MOSFETs are turned on and off by a control voltage applied between a source contact and a gate contact. In practice, the control voltage is applied between the source connection and the gate connection. The wire leading to the source contact has an inherent inductance which has the effect that the load current which changes with respect to time during the switching-on or switching-off of the MOSFET induces a voltage in the inductance which counteracts the control voltage in a switching-delaying manner. If a plurality of MOSFETs are connected in parallel and driven jointly from a single voltage source, then the aforementioned inductance causes high-frequency oscillations to occur in the drive circuit, owing to unavoidable component tolerances, with amplitudes that can destroy the MOSFET. The oscillation frequency is critically determined by the inductance of the source connection and, in addition, by other parasitic network and component parameters. In order to reduce the disadvantages of the effect of the inductance of the source connection, European Patent EP 0 265 833 B1 proposes disposing the interconnects which are connected to the source connections on one side of the MOSFET and the interconnects for driving on the other side of the MOSFET. This results in extensive magnetic decoupling of the drive circuit from the source connections of the semiconductor component.
Consequently, it is predominantly the leakage inductances in the leads to the load current connections of one or more semiconductor switches which pose problems, i.e. over-voltages, particularly in the case of very high rates of current rise (dI/dt). Large capacitors and resistors are necessary, therefore, in order to compensate for the over-voltages. However, the capacitors and resistors can adversely affect the switching behavior of the semiconductor components. In order to avoid these disadvantages, it is endeavored in practice to reduce the inductances in the leads by skillful, i.e. short, interconnect routing.
It is accordingly an object of the invention to provide low-inductance semiconductor components that overcome the above-mentioned disadvantages of the prior art devices of this general type, which does not have the disadvantageous effect of the leakage inductances and can be produced in a simple manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, a semiconductor component. The semiconductor component contains a carrier plate, a housing connected to the carrier plate and having a first side and a second side opposite the first side, and at least one ceramic substrate having a top side and a metallization layer disposed at least at the top side. The ceramic substrate is supported by the carrier plate. At least two switching elements are disposed at the top side of the ceramic substrate and each have load current connections and a control connection. The two switching elements are disposed next to one another. A plurality of external load current connection elements are disposed on the first side and the second side of the housing. Leads connect the external load current connection elements electrically to the load current connections of the switching elements. The leads are disposed substantially parallel to each other, and adjacent ones of the external load current connection elements each have an opposite polarity, so that adjacent ones of the leads each carry opposite current directions. First terminals for receiving a first supply potential are connected to some of the external load current connection elements. Second terminals for receiving a second supply potential are connected to others of the external load current connection elements not connected to the first terminals. The two switching elements include a first switching element connected to a first of the external load current connection elements on the first side of the housing and the first external load current connection element is connected to one of the first terminals. The first switching element is further connected to a second of the external load current connection elements on the second side of the housing and the second external load current connection element is connected to one of the second terminals. The two switching elements have a second switching element connected to a third of the external load current connection elements on the second side of the housing and the third external load current connection element is connected to one of the first terminals. The second switching element is further connected to a fourth of the external load current connections on the first side of the housing and the fourth external load current connection element is connected to one of the second terminals.
To put it another way, the leads of two adjacent switching elements are disposed in such a way that magnetic fields produced in the leads are mutually compensated by the opposite polarity at the load current connection elements and the effective inductance is thereby minimized.
It is furthermore provided that a switching element is connected to the two leads, the leads extending between the first and second sides of the housing and one lead having the first supply potential and the other lead having the second supply potential.
It is furthermore provided that the first and, respectively, the second supply potential are applied to the load current connection elements which are situated on one housing side and are assigned to two adjacent switching elements. In order to obtain a minimal leakage inductance, it is consequently necessary to provide at least two adjacent switching elements whose load current connection elements which are adjacent on one housing side have a different polarity. The advantages of the invention can be achieved with any even number of switching elements. The multiplicity of even-numbered switching elements are advantageously disposed next to one another on an alignment line. The leads between the load current connection elements and the load current connections of the switching elements that are disposed next to one another advantageously run approximately orthogonally with respect to the alignment line. The assigned load current connection elements then alternately have the first and the second supply potential. In addition to the low leakage inductance, a very compact construction of the semiconductor component can be achieved as a result of this. Only little area need be provided for suitable interconnect routings or for the leads, which enables a cost-effective construction.
A switching element preferably contains two semiconductor switches which are serially connected to one another and whose junction point is connected to a load current connection element and forms an output of the semiconductor component.
The two serially connected semiconductor switches are preferably disposed on an alignment line that is approximately orthogonal with respect to the first and, respectively, the second side. A half-bridge is thereby formed in a known manner.
It is furthermore conceivable for the multiplicity or part of the multiplicity of switching elements or half-bridges to be connected in parallel by the metalization layer and/or bonding wires in order to increase the current-carrying capacity of the semiconductor component. This enables the use of high power ranges.
MOSFETs or IGBTs are preferably used as the switching elements. However, any desired controllable semiconductor switch can be used, in principle. The invention is preferably used for driving a phase of a 3-phase invertor module. The semiconductor component then constitutes a very low-inductance half-bridge.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in low-inductance semiconductor components, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.